// Copyright (C) Kumo inc. and its affiliates.
// Author: Jeff.li lijippy@163.com
// All rights reserved.
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
//
#pragma once

#include <boost/random/uniform_int_distribution.hpp>
#include <pollux/testing/expression/arg_types_generator.h>

namespace kumo::pollux::exec::test {

class FloorAndRoundArgTypesGenerator : public fuzzer::ArgTypesGenerator {
 public:
  std::vector<TypePtr> generateArgs(
      const exec::FunctionSignature& signature,
      const TypePtr& returnType,
      FuzzerGenerator& rng) override {
    if (signature.argumentTypes().size() == 1) {
      return generateSingleArg(returnType, rng);
    }
    POLLUX_CHECK_EQ(2, signature.argumentTypes().size());
    return generateTwoArgs(returnType);
  }

 private:
  // Generates a decimal type following below formulas:
  // p = p1 - s1 + min(s1, 1)
  // s = 0
  std::vector<TypePtr> generateSingleArg(
      const TypePtr& returnType,
      FuzzerGenerator& rng) {
    const auto [p, s] = getDecimalPrecisionScale(*returnType);
    if (s != 0) {
      return {};
    }

    const auto s1 = rand32(38 - p + 1, rng);
    if (s1 == 0) {
      return {DECIMAL(p, 0)};
    }

    return {DECIMAL(p - 1 + s1, s1)};
  }

  // Generates a decimal type and an integer type. Decimal type is generated
  // following below formulas:
  // p = p1 + 1
  // s = s1
  std::vector<TypePtr> generateTwoArgs(const TypePtr& returnType) {
    auto [p, s] = getDecimalPrecisionScale(*returnType);
    if (p == 1 || p == s) {
      return {};
    }

    return {DECIMAL(p - 1, s), INTEGER()};
  }

  static uint32_t rand32(uint32_t max, FuzzerGenerator& rng) {
    return boost::random::uniform_int_distribution<uint32_t>()(rng) % max;
  }
};

} // namespace kumo::pollux::exec::test
